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By Ray Brainard

Treated effluent from the Clean Water Coalition (CWC) member agencies is currently discharged at an annual average rate of 6,570 l/s into the Las Vegas Wash, and is increasing annually. As the effluent flow increases, the nutrient loading of the treated effluent will approach the maximum limits allowed under the current regulations. To manage this flow while maintaining water quality in Lake Mead, the CWC is implementing a 44-km-long conveyance system. This paper discusses the geological and geotechnical aspects of the 13.4-km-long tunneled section through the River Mountains and their effect on design. The tunnel alignment traverses a heterogeneous package of volcanic and sedimentary rocks exhibiting widely variable rock conditions.

Jan 1, 2008

By W. Lee Daniels

Significant deposits (> 4,000 ha) of heavy mineral sands were discovered in the USA Coastal Plain of Virginia and North Carolina in 1989. The majority of these lands support highly productive row crop agriculture, and the development of restoration protocols that would return these lands to agricultural use was deemed to be critical to the long term sustainability of mining operations. Virginia Tech worked closely with all stakeholders to develop appropriate restoration protocols and to coordinate their implementation. Full-scale mining operations at the Old Hickory Project in Virginia were initiated in 1997 by Iluka Resources Inc., and restoration protocols have continued to evolve in response to a variety of economic, technical, and social issues. Approximately 750 ha of land are in various phases of backfilling and final reclamation. Return of these lands to agricultural row-crop production has been complicated by lateral variability in mine soil physical conditions, excessive compaction, and limited topsoil return. However, within the past two years, a series of tailings deposition and soil reconstruction practices have been developed and implemented that significantly improve post-mining soil productivity. Deep ripping and appropriate use of organic soil amendments have been particularly effective at restoring post-mining soil productivity.

Jan 1, 2005

By S. Fawell, H. R. Manouchehri

The main electrophysical properties, i.e., dielectric constant and electrical conductivity, of pure calcite, quartz and wollastonite mineral samples were measured and their triboelectric charge attributes were investigated by contacting minerals particles with different tribochargers made from different materials. In addition the energetic work function values for mineral samples were estimated due to their acquisition charge. Besides, the behaviour of triboelectrically charged of different particle size fractions of mineral samples were inferred. Finally an attempt were made to translate the findings from single mineral systems to a real carbonate ore. The results exposed good prospects to beneficate the examined minerals by triboelectric separation.

Jan 1, 2002

By L. Mukka

The existing main mine ventilation system for the production areas to the Kiruna mine was constructed during the period 1994-1996 and extended with 4 more shafts, including fan stations, for the sea ore body from 1997-1998. Two papers have been presented from this project at the 7th US Mine Ventilation Symposium in 1995 and at The 6th International Mine Ventilation Congress in 1997. In 2005, pre-studies for a new main haulage level were started. Different haulage methods were presented including ventilation systems. The pre-studies showed that the existing ventilation system, including fan stations for the new main haulage system in the production area, could be extended. However, a new system for the central area, which was not in the initial investment program, would be needed. In the beginning of 2006, a decision was made to design a new ventilation system for the central area to make it possible to get air to the development work for the new main haulage system, independent of the haulage method. This system was operational by the beginning of 2007. The new main haulage system, which was decided to be located on level 1365 m, only requires that the existing shafts be extended - the capacity of the fans seems to be enough. However, the problem is that the existing level 1045 m and the new level 1365 m have to be in operation in parallel for approximately 7-8 years. The challenge for the moment is determining how to ventilate the production areas for both levels at the same time, while simultaneously constructing the extended system. This paper will describe the problems associated with the extension of the main ventilation system and some potential solutions for these problems. The new main haulage level 1365 m must be in operation by 2012.

Jan 1, 2009

By G. Deschênes

Following a successful investigation on the Central Zone sample, a cyanidation study was conducted on an ore sample from the AD-MW Zone of Clarence Stream Property, owned by Freewest Resources Canada, to develop a leaching strategy to extract gold. At a grade of 6.48 g/t, gold is present in the forms of aurostibite, free gold and electrum. The ore contains 4.3% berthierite/gudmundite, 1.3% pyrrhotite, 0.7% pyrite, 0.07% stibnite and 0.9% arsenopyrite. Similar to the Central Zone, the extraction of gold from the AD-MW Zone can be performed at atmospheric pressure, pH 10.5 and with a low concentration of cyanide. The grind size had no effect on gold extraction between a P80 of 28 to 71 µm. The oxygen and cyanide requirement significantly increased with a ?ner grind. Consequently, a very close control of cyanide addition is required to minimize passivation of gold. Lead nitrate, added in the pretreatment, increased the extraction of gold by 2.3%. Leaching at pH < 10 improved gold extraction but increased the cyanide consumption by 5%. Passivation of gold occurred when the pretreatment was longer than 2 hours. A longer pretreatment reduced the cyanide consumption by 5%. Mineralogical characterization of the leach residue with no gravity pretreatment prior to leaching indicated the presence of unleached gold grains and passivated gold grains. Removal of coarse gold by gravity increased the extraction by 2.8% (leach residue at 0.74 g/t Au). Increasing the DO to 16 ppm or the lead nitrate from 500 to 1,000 g/t increased the overall gold extraction to 90.4% (leach residue at 0.62 g/t), which is the maximum gold extraction obtained. The leaching parameters were 800 ppm NaCN, DO 16 ppm and pH 10.5 for a duration of 120 hours. The associated cyanide consumption was 4.0 kg/t. Gold leaching was not sensitive to cyanide concentration. Reducing the cyanide concentration to 250 ppm resulted in a gold extraction of 89.5% with a cyanide consumption of 2.6 kg/t.

Jan 1, 2009

By Dianne C. Marozas

The U.S. Bureau of Mines is conducting research to evaluate the potential for developing an in situ leach mining process that will selectively extract manganese from oxide ores, leaving gangue relatively undisturbed. To accomplish this, a geochemical approach, based on deposit-specific information such as mineralogy and geology, is used to constrain the operating parameters of the system. Among the studies being conducted are (1) leaching experiments to define reaction mechanisms and kinetics, (2) detailed petrologic characterization at the microscopic scale to assess Mn distribution and leaching efficiencies, (3) deposit characterization and evaluation, and (4) development of potential Mn recovery schemes. Data from these studies are being used to develop engineering design information for an in situ mining process. Specific details of the Bureau&apos;s research project are discussed, including results obtained to date.

Jan 1, 1991

By H. Mischo, R. Ellmies

Uranium has been mined in Namibia since the 1970s. The worldwide increasing need for energy in the early 2000s has led to the development and opening of a second uranium mine in 2007 and has triggered an increased interest in uranium exploration, often referred to as “the Namibian Uranium Rush.” In all, four mining licenses have been granted by the Namibian Government, which currently has two mines in operation, a third undertaking trial mining and the fourth in project finance negotiations. In addition, highly intensive prospecting activities at additional deposits are at an advanced stage. The finalization of the strategic environmental impact assessment (SEA) on uranium mining in 2010, the first of its kind and scale in the world, has enabled the Namibian government to assess this uranium rush and its tremendous legal, socioeconomic and environmental impacts and to prepare for the different future scenarios conceivable when this article was written in 2011, including both a skyrocketing and a complete breakdown of demand scenario. The Fukushima disaster and plans of the Namibian government to significantly increase royalties and company taxes in 2011 have threatened the market situation, forcing investors to reevaluate Namibian uranium mining projects. However, with the tax and royalty increase initiative since withdrawn, most projects are back on track at this point in time.

Jan 1, 2012

By Y. K. Yen, J. D. Miller, C. L. Lin

The image-based On-line Particle Size Analyzer (OPSA)system has been developed at the University of Utah to measure particle size distributions under plant conditions where overlapped and segregated particles are being transported on a moving belt conveyor. Evaluation of the OPSA system at several plant sites has been completed. The results show a consistent agreement between the particle size distributions obtained from the OPSA system and those obtained from laboratory screen analysis of belt samples. These results and the stable performance of the OPSA system during the field tests suggest that continuous quality control of crushed products is possible using the OPSA system.

Jan 1, 1999

By D. Meadows, P. Carrato, E. Wingate, K. Churchill

Extracting lunar ice, to be processed into pure water or hydrolyzed into oxygen and hydrogen, faces many challenges. On the Moon icy-regolith deposits that contain up to 10% water are found within Permanently Shadowed Regions (PSR) at both lunar poles, where temperatures approach -220 ⁰C. NASA has identified several technology gaps that exist in developing these resources including: • Excavating large quantities of icy-regolith • Delivering large quantities of acquired resources • Hardware that is lightweight and energy efficient • Hardware that is reliable and durable. NASA uses public challenges to incentivize innovative approaches to closing these gaps. The Break the Ice Lunar Challenge provides over three million dollars in prize money to teams that compete in developing solution to mining the Moon. This paper describes the rules for this challenge and presents some of the proposed solution.

Feb 1, 2023

By B. Cousins

Copper, nickel, zinc and other ?penalty? metals are found with gold together in nature, and have a similar chemical affinity for cyanide used in leaching operations4. As a result, solutions that come from the heap leach pads contain a significant concentration of penalty metals along with the desired gold. In solution, gold and cyanide form the complex Au(CN)2- that is readily adsorbed onto activated carbon. Penalty metals as individual metal ions also load onto activated carbon and, depending on the concentration of cyanide and the pH of the solution, can form various cyanide complexes. Some of these complexes can also load onto carbon while some are significantly inhibited from loading. Copper, for example, can form the dicyanide complex Cu(CN)2-, the tricyanide complex Cu(CN)32-, and the tetracyanide complex Cu(CN)43-. At a low pH and a low concentration of cyanide, the dicyanide complex predominates. At a higher pH and a higher concentration of cyanide, the tetracyanide complex predominates. Without excess cyanide, however, individual copper ions can remain present. Activated carbon is used in gold extraction because it is highly selective for gold and less so for other metals, such as copper3. However, copper has the ability to adsorb (?load?) onto activated carbon and block the adsorption of gold when it is in the dicyanide form and in a high enough concentration. When copper is in the tetracyanide form, copper loading is significantly inhibited, allowing for the maximum gold recovery. In order to ensure the tetracyanide complex is formed, a combination of both available cyanide and elevated pH must be present. In the South Area of Newmont Mining Corporation?s Gold Quarry mine in Carlin, Nevada, copper and nickel loading becomes a problem when certain acid generating zones of the heap are leached. Copper, nickel, zinc and other penalty metals become leachable and the lower pH uses up more of the cyanide and creates carbon loading conditions for the metals. This decreases the carbon?s ability to extract the gold from solution, decreasing the recovery and increasing the concentration of gold in the barren solution that leaves the carbon columns. In this study, operational data from March through to May of 2007 is presented to show how Newmont developed a quick fix to lower pH and elevated metal concentrations that were causing low gold loadings on activated carbon at their South Area Leach (SAL) heap leach operations. Laboratory tested were also conducted to examine the chemical kinetics of metal loading and the individual effects of increased cyanide concentrations. THEORY Copper I ions form four different complexes with cyanide in solution: the monocyanide species CuCN, the dicyanide species Cu(CN)2-, the tricyanide species Cu(CN)32-, and the tetracyanide species Cu(CN)43-. The species are formed from the following reactions: [Cu)(?+-+ K1 (1) Cu ß2 (2) --+?+23)(3CNCuCNCu ß3 (3) --+?+34)(4CNCuCNCu ß4 (4) ] where K1 equals 1019.50, ß2 equals 1024.03, ß3 equals 1028.65, and ß4 equals 1030.35. Along with these complexing reactions, hydrogen cyanide and water also dissociate in solution, as per the following reactions: [H?+-+ KH (5) OHOHH2?+-+ KW (6)] where KH has a value of 109.24 and KW has a 1014 value2. These six chemical equations compete with each other, with domination of one over the others dependent on the CN- and H+ concentrations. Each complex also has different properties when it comes to its loading behavior on activated carbon. The dicyanide copper complex and the monocyanide copper complex have an affinity for adsorption onto activated carbon that is greater than the affinity of gold cyanide for adsorption. They also have a lower solubility in water, which enhances adsorption. The tricyanide copper complex and the tetracyanide copper complex are water soluble and have an affinity for loading adsorption on activated carbon that is less than the affinity of gold cyanide for loading adsorption1. There are three prime reasons for this phenomenon. First, the extra cyanides mask the metal ion more, which blocks the main adsorption characteristic of the complex. Second, the complexes are also larger, making it harder to physically fit into the active sites on the carbon. This helps make the latter two complexes kinetically inhibited from adsorption, freeing carbon active site to load with gold cyanide complexes. Third, it is also important to consider the expressions of the mass and charge balance. These balances describe all the overall concentration of copper and cyanide in solution, as well as marking overall charges of the ions in solution4. This is important because significantly changing the charge from positive/neutral to more negative is another reason for activated carbon to reject adsorbing the higher cyanide complexes. The speciation of copper and other penalty metal cyanide complexes in solution is dependent on the pH. At lower pH values, increased hydrogen ions (H+) can out-compete metals for cyanide ions. Lower free cyanide in the system leads to the lower cyanide species of copper cyanide predominating, with a noticeable concentration of the free metal, monocyanide and dicyanide species of copper cyanide. At higher pH values, hydrogen ions are significantly reduced, reducing the kinetics of HCN formation. More free cyanide remains in the system, allowing for more complexing. With this higher amount of cyanide in the system, the tetracyanide species of copper cyanide predominates, also with a noticeable concentration of the tricyanide species of copper cyanide. Higher copper concentrations, however, require more

Jan 1, 2009

By Donald D. Murphy

My first contact with underground, bolt conveyors came when I was hired as a draftsman by the La-Del Conveyor & Manufacturing Company in 1935. At that tine relatively few nines were using haulage belt conveyors. Wore they were in use, they were usually loaded by chain or shaker type room conveyors which in turn were hand loaded at the working face. Duo to the low room tonnage, a gathering belt might receive who output of from six to eight rooms. For several years belts 26 and 30" in width were the favorites for coal mine use. Belt speeds very seldom exceeded 200 ft. per mm. at that time. Conveyor lengths for the majority of units lay between 1.000 and 2000 ft. For a number of years 25 H.P. drives were adequate for those conveyors. From 1940 until about 1950 loads and speeds went up slightly and 40 H.P. drives became the standard. Since the majority of mines were then using direct current power systems, we were able to use controllers with 3 or more steps of starting resistance. The slow belt speeds coupled with relatively long starting cycles kept the rate of acceleration low and gave us smooth, easy starts.

Jan 1, 1963

By S. Yerel

In a mineral processing plant, the determination of a preventive maintenance schedule is one of the most important maintenance policies. In this study, to determine the preventive maintenance schedule for the Emet Colemanite Mineral Processing Plant in Turkey, a mean quality control chart was constructed using the historical concentrate B2O3 grade data. The effect of preventive maintenance scheduling on B2O3 grades was monitored using the mean quality control chart. It was determined that recovery increased after each preventive maintenance scheduling. Close examination of the mean quality control charts indicated that there were three periods that showed different grade characteristics. These were identified as the period ?prior to preventive maintenance,? the period ?after preventive maintenance? and the period ?requiring preventive maintenance.? These periods were compared as two independent samples by using the Kolmogorov-Smirnov test. Application of this test for interpretation of the mean quality control chart enabled the authors to analyze the system effectively, and it showed that the preventive maintenance for this plant should be scheduled at four-month intervals.

Jan 1, 2007

By Shigeru Nishitake

The Earth Pressure Balanced (EPB) shields designed by Mitsubishi Heavy Industries, Ltd., are recently more enthusiastically accepted by tunnel boring specialists. This company having built 1,000 tunnel shields utilizes its vast experience to resolve the problem to excavate through big boulders scattered in rather soft alluvial soil. Several types of EPB shields which can cope with large size boulders are described. Such shields are equipped with both drag bits and rolling disc cutters on the cutterheads. Previously removal of boulders has presented safety problems for workers while in the muck chamber, or venturing in front of the shield. This report describes the problem and how the equipment was modified to deal with the problem.

Jan 1, 1987

From a vast army of workers to gargantuan machines to immense volumes of material being moved, almost everything about the Port of Miami Tunnel (POMT) project points to tunneling on a massive scale. Almost.The star of this underground and underwater show is a Herrenknecht tunnel boring machine (TBM,) nicknamed ?Harriet? by a local Girl Scout troop. With her 12.9-m- (42.3-ft-) diameter cutting head and a total length of 139 m (457 ft), Harriet is boring through thousands of cubic meters of clay, dirt and sand, which is often mixed with coral and other materials, to create two 1,280-m (4,200-ft) traf?c tunnels connecting Watson Island and the Port of Miami (Dodge Island) beneath Biscayne Bay, FL. But in the midst of all of the oversized equipment and machines, a strong contender for the best supporting nod goes to a relatively tiny machine: the Brokk 400. Bouygues Civil Works Florida crews are using the compact, remote-controlled and electric-powered machine to excavate five cross passages between the twin traffic tunnels. The pas-sages will be essential to the safety of people who drive their vehicles under the bay every day.

Sep 1, 2013

By Brian Fulcher

The Arrowhead Tunnels Project represents the final portion of a 70 km (44-mile) long water conveyance facility that will bring up to 28 m3/sec (1,000 ft 3/sec) of water into Southern California. The 13 km (8-mile) tunnelling project is well underway and consists of two, 5.8 m (19-ft) diameter TBM bores through extremely variable geological conditions. An extensive and essential pre-excavation drilling and grouting program was performed in all reaches of the Arrowhead Tunnels Project, located north of San Bernardino, CA. This program supported the advance of two hybrid hard rock TBMs though extremely challenging ground conditions under substantial ground cover and up to 27 bar (900 ft) of ground water pressure. The well known San Andreas Fault lies nearby and has greatly influenced the local geological conditions. This paper will describe the means, methods and materials used throughout the numerous phases of the pre-excavation grouting program. It will also describe many versatile, flexible and innovative drilling and grouting methods and equipment systems utilized to improve performance, save time and costs in constantly changing geological conditions. Considerable lessons learned have been learned while overcoming some extremely formidable ground conditions and safely advancing the tunnels.

Jan 1, 2008

The primary use of coal in the US is for electric generation. The problems associated with the use of this vast amount of coal is the central theme of these sessions. The problems discussed include: production capacity, mining problems, coal cleaning, transportation, combustion, and various environmental problems, such as health effects of coal combustion, water and air pollution, and solid waste disposal.

Jan 1, 1979

By Christopher J. Bise

INTRODUCTION A mine&apos;s power system represents the driving force behind all of the extraction and auxiliary operations, because the production and transportation of mined material and the operation of equipment, such as fans and pumps, are all dependent upon a power source. Once, compressed air was the primary power source in mining; today, however, electrical power dominates. This chapter reviews the basic theories of com- pressed-air and electrical power and provides several examples of applications in mine power systems. COMPRESSED-AIR POWER General Compressed air has been, and should continue to be, an important source of power in mining operations. It has been used as a means of blasting coal in conventional mining and is widely used to operate stopers, mucking machines, and other air tools in both coal and hard-rock mines. Such applications demonstrate the suitability of compressed air for applications requiring linear motion, but it is also utilized for its reliability and safety. A compressed-air system is composed of a compressor, a receiver, a distribution network, and the air-operated machines. A compressor takes in air at normal atmospheric pressure (free air) and compresses it to a higher discharge pressure. The discharge pressure must be high enough to overcome the friction in the distribution system of pipes and hoses and deliver the compressed air to the machines at the pressure recommended by the manufacturer. The most common type of compressor used in mines is the reciprocating compressor in which the air is compressed by a piston in a cylinder. An air receiver is a container or storage tank that is located in the distribution system between the compressor and the machines. It stores compressed air, when the full capacity of the compressor is not being used, and gives a more steady flow of air to the machines. The distribution network consists of pipes, Oalves, elbows, tees, and hoses that transmit the compressed air from the receiver to the machines in the mine. It is essential that the distribution system be designed with the proper sizes and lengths of pipe, hose, and other components to keep pressure losses well within allowable limits. The air-operated machines consist primarily of drifters, stopers, pluggers (sinkers), slushers, and several other pieces of equipment. Compressor Operation Every compressor is made up of one or more basic elements; a single element, or a group of elements in parallel, comprises a single-stage compressor. Many compression problems involve conditions beyond the practical capability of a single compression stage. Too great a compression ratio (absolute discharge pressure divided by absolute intake pressure) may cause excessive discharge temperatures or other design problems. It, therefore, may become necessary to combine elements or groups of elements in series to form a multi- stage unit, in which there will be two or more steps of compression. The number of stages commonly used in reciprocating compressors is as follows: Pressure Number of stages 0- 150 pig 1 80- 500 psig 2 500-2500 psig 3 2500-5000 psig 4 When pressure is referred to as pounds per square inch gage (psig), it means the pressure (in pounds per square inch) above barometric pressure as measured by a gage. The sum of barometric pressure and gage pressure is the absolute pressure (in pounds per square inch). The gas is frequently cooled between stages to reduce the temperature and volume entering the subsequent stages, thereby reducing the work required for compression. The basic reciprocating compression element is a single cylinder compressing on only one side of the piston (single-acting). A unit compressing on both sides of the piston (double-acting) consists of two basic single-acting elements operating in parallel in one casing. The reciprocating compressor uses automatic spring-loaded valves that open only when the proper differential pressure exists across the valves. Intake valves open when the pressure in the cylinder is slightly below the intake pressure. Discharge valves open when the pressure in the cylinder is slightly above the discharge pressure. In Fig. 1, Diagram A shows the basic element with the cylinder filled with air at atmospheric pressure. On the corresponding theoretical pressure-volume

Jan 1, 1986

By Douglas B. Silver

Super Cycle future The final topic is mining?s future. The most important questions are ?How much longer is the Super Cycle going to last? What should we expect to see going forward? How will the Super Cycle end?? Three possible scenarios follow. Scenario one: Super Cycle has peaked Kathy Casey-Kirschling is officially the first Baby Boomer. She was born Jan. 1st, 1946. If you google ?first baby boomer,? she?s the one that shows up. A Baby Boomer is anybody born between 1946 and 1964. In the United States, it represents about a quarter of the population ? approximately 76 million people. The Baby Boomer generation is going to change the economics of the world because there are so many in the generation. A review of spending patterns indicates that the largest amount of discretionary spending occurs between the ages of 49 and 52. Retired people tend to live on fixed incomes so they have less discretionary income. They also tend to downsize their house, which may contribute to the housing glut and the need for a lot less metal. Therefore, the upcoming retirement of the Baby Boomer generation could result in a massive shift in economic spending resulting in the peaking of the Super Cycle. Figure 1 is an index graph from the Toronto Stock Exchange (TSX). The index has recently peaked. A lot of people see that as a sign that bad things coming our way. A careful review of different commodity prices also suggest that the peak has occurred and it does not seem to matter which commodity prices are considered. Copper prices have seen a peak as have nickel prices. Nickel and molybdenum displayed the same trend with a peak in 2005 as did zinc. Uranium, which has single-handedly tried to behave like the dot com craze, has also peaked.

Jan 1, 2008

By William P. Blacutt

This paper describes the strategy, the struggles, and the obstacles encountered during the last two years in the ongoing process to capitalize Vinto. The effort involves the offering of a vertically integrated business package composed of the tin and antimony smelters along with the two principal tin mines of the country. Capitalization: Bolivia&apos;s Innovative Approach for Privatization, the Vinto Case provides a summary of hard-earned lessons. These experiences can be success- fully implemented in other nations committed to transforming their state natural resource sector.

Jan 1, 1998

By Lawrence H. Roth

Past failures of coal refuse embankments have resulted in intensified efforts in inspections of coal refuse sites by the Mining. Enforcement, and Safety Administration (MESA). MESA inspections however, are mainly qualitative and are often time consuming, Therefore, in August 1975 CH2M HILL was awarded a contract to identify, develop, and test a rapid system for monitoring coal refuse embankments to aid in MESA inspections. The rapid monitoring system developed uses convergent and vertical photography from conventional fixed-wing aircraft. The system was tested on an active landslide and on two coal refuse facilities using both black and white and color infrared film. Field tests showed the system was capable of accurate measurement while providing qualitative data through photo interpretation. The accuracy of the system allows it to be used to monitor coal refuse embankments, tailings dams, major earth dams, and natural slopes. Based on CH2M HILL results cost for monitoring by rapid system was approximately 25 percent of cost by conventional ground survey.

Jan 1, 1980